The following is a list of symptoms in descending order of probability that the person observed is driving while intoxicated. The list is based upon research conducted by the National Highway Traffic Administration:

• Turning With a Wide Radius
• Straddling Center of Lane Marker
• "Appearing to be Drunk"
• Almost Striking Object or Vehicle
• Weaving
• Driving on Other Than Designated Highway
• Swerving
• Speed More Than 10 mph Below Limit
• Stopping Without Cause in Traffic Lane
• Following Too Closely
• Drifting
• Tires on Center or Lane Marker
• Braking Erratically
• Driving into Opposing or Crossing Traffic
• Signalling Inconsistent with Driving Actions
• Slow Response to Traffic Signals
• Stopping Inappropriately (Other Than in Lane)
• Turning Abruptly or Illegally
• Accelerating or Decelerating Rapidly
• Headlights Off

Speeding, incidentally, is not a symptom of DUI; because of quicker judgment and reflexes, it may indicate sobriety.